Chronic beryllium disease (CBD) is a granulomatous lung disorder caused by beryllium exposure in the workplace and is characterized by the accumulation of beryllium-specific CD4+ T cells in the lung. Disease susceptibility has been linked to HLA-DPB1 alleles, including DPB1*0201, that possess a glutamic acid residue at position 69 of the HLA-DP2 2-chain (2Glu69). We have shown that beryllium directly binds to HLA-DP2 molecules and that the majority of beryllium-specific CD4+ T cells recognize beryllium in the context of HLA- DP. Importantly, the DP molecules that present beryllium match those implicated in disease susceptibility, confirming that the HLA contribution to disease is based on the ability of those molecules to bind and present beryllium to T cells. We have recently crystallized HLA-DP2 and identified a potential beryllium binding site involving ?Glu69 and two other invariant glutamic acids at positions ?26 and ?68. Functional studies confirmed that beryllium recognition was dependent on this cluster of negative charges. To date, no animal model of beryllium-induced disease exists. Previous attempts to generate a murine model failed to document a beryllium-specific adaptive immune response. Importantly, mice lack a major histocompatibility complex class II (MHCII) molecule of similar sequence and structure to HLA-DP2. Thus, we hypothesize that the generation of a humanized transgenic mouse containing the cluster of negative charges unique to HLA-DP2 will result in a disease-specific murine model with pathology reflective of the human disease. HLA-DP2 and -DP4 transgenic mice on an FVB/N background have been generated by researchers at NIOSH. However, these mice express murine MHC and lack human CD4, an important coreceptor for optimal T cell activation. No studies characterizing the response of these mice to inhaled beryllium have been published. Preliminary data show peribronchovascular mononuclear cell infiltrates occurring only in beryllium-exposed HLA-DP2 transgenic mice after beryllium oxide (BeO) exposure, strongly suggesting that the inflammatory response is due to the presence of the HLA-DP2 transgene and supporting our hypothesis that ?Glu69-containing HLA-DP molecules are required for the generation of a murine model of beryllium-induced disease. In the first specific aim, we will re-derive the HLA-DP2 transgene in C57BL/6 mice lacking murine MHCII molecules and expressing human CD4. In the second aim, we will directly compare the beryllium-induced adaptive immune response in these animals and DP2-expressing FVB/N mice, testing the hypothesis that stabilization of the interaction between HLA-DP2 and T cell receptor with the human CD4 coreceptor and elimination of the confounding effects of mouse MHCII will optimize the beryllium-specific immune response. Together, these studies will lead to a disease-specific murine model, targeting the exact molecule necessary for the development of a human disease.
The development of an HLA-DP2 transgenic mouse model of beryllium-induced disease will enhance our ability to define the precise environmental antigen causing a human granulomatous lung disease and to determine how metal antigens trigger an immune response.
|Mack, Douglas G; Falta, Michael T; McKee, Amy S et al. (2014) Regulatory T cells modulate granulomatous inflammation in an HLA-DP2 transgenic murine model of beryllium-induced disease. Proc Natl Acad Sci U S A 111:8553-8|